Ikea Besta wall rail mounting problems

Hello,

I bought 4 120 Besta cabinets and mounted them with 8 wall rails (in a row one behind the other). Everything is horizontal. But when I hung the cabinets, they are not flush at the front or at a 90° angle to the wall. I suspect the wall is 100% straight since it is a building from 1950. According to the instructions, you can only adjust to the left or right!!! How can I get this problem under control? I wanted to avoid using a wooden strip because then the glass shelves on top would no longer be flush??? I was maybe thinking of using washers to adjust the rails!?

Can someone help me?

Thanks

What does it mean that the glass panels on top are no longer flush?

When several carcasses with glass panels are placed or mounted side by side, the glass panels do not touch each other 100%, but there is about 1mm of air between each glass panel.

The surface on top or the place where the end of one carcass and the beginning of the next carcass meet should be aligned in a straight line. The entire surface on top will not be 100% flat overall, because the top and bottom panels are not 100% straight. I once explored that. Usually the glass panel bends slightly in the middle and a slight dip forms, which is not visible. However, the transitions from one glass panel to the next must be aligned.

You just have to make sure that when mounting on a wall, the wooden top panels and wooden bottom panels of the Besta carcasses are aligned and thus also the fronts. If this is not the case because the wall is crooked, I would hang the individual carcasses, align them flush with each other, and then drill through from one carcass to the next with a 5mm wood drill bit (use a pre-drilled hole for the shelf insert, as there is a chipboard panel inside the carcass!!) and then screw them together with carcass connector screws from the hardware store. This way the carcasses can no longer sag. For each carcass I would use at least 2 carcass connectors, each in the 3rd hole from below and the 3rd hole from above. If possible, 4 carcass connectors: 3rd hole from below front and back, 3rd hole from above front and back.

Then lay the glass panels on top. Done.

If I have understood the problem correctly, the carcasses hang on the wall slanting downwards at the back. To compensate for this, something would need to be placed under the rail. The carcasses would then have a gap from the wall at the top, and the glass panel would no longer align with the carcass at the front if it rests against the wall. If you place a wide board underneath that extends over the carcass to the thickness of the glass panel, then the board forms the stop for the panel. With a quarter round molding, you could cover the board and part of the glass panel.